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Title: Br{sub 2} molecular elimination in 248 nm photolysis of CHBr{sub 2}Cl by using cavity ring-down absorption spectroscopy

Abstract

Elimination of molecular bromine is probed in the B {sup 3}{pi}{sub ou}{sup +}<-X {sup 1}{sigma}{sub g}{sup +} transition following photodissociation of CHBr{sub 2}Cl at 248 nm by using cavity ring-down absorption spectroscopy. The quantum yield for the Br{sub 2} elimination reaction is determined to be 0.05{+-}0.03. The nascent vibrational population ratio of Br{sub 2}(v=1)/Br{sub 2}(v=0) is obtained to be 0.5{+-}0.2. A supersonic beam of CHBr{sub 2}Cl is similarly photofragmented and the resulting Br atoms are monitored with a velocity map ion-imaging detection, yielding spatial anisotropy parameters of 1.5 and 1.1 with photolyzing wavelengths of 234 and 267 nm, respectively. The results justify that the excited state promoted by 248 nm should have an A{sup ''} symmetry. Nevertheless, when CHBr{sub 2}Cl is prepared in a supersonic molecular beam under a cold temperature, photofragmentation gives no Br{sub 2} detectable in a time-of-flight mass spectrometer. A plausible pathway via internal conversion is proposed with the aid of ab initio potential energy calculations. Temperature dependence measurements lend support to the proposed pathway. The production rates of Br{sub 2} between CHBr{sub 2}Cl and CH{sub 2}Br{sub 2} are also compared to examine the chlorine-substituted effect.

Authors:
; ; ; ; ; ;  [1];  [2]
  1. Department of Chemistry, National Taiwan University, Taipei 106, Taiwan and Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 106, Taiwan (China)
  2. (China)
Publication Date:
OSTI Identifier:
20868216
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 126; Journal Issue: 3; Other Information: DOI: 10.1063/1.2426334; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ABSORPTION SPECTROSCOPY; BROMINATED ALIPHATIC HYDROCARBONS; BROMINE; CHLORINATED ALIPHATIC HYDROCARBONS; DISSOCIATION; EXCITED STATES; MASS SPECTRA; MOLECULAR BEAMS; PHOTOCHEMISTRY; PHOTOLYSIS; PHOTON-MOLECULE COLLISIONS; POTENTIAL ENERGY; REACTION KINETICS; TEMPERATURE DEPENDENCE; TIME-OF-FLIGHT MASS SPECTROMETERS; TIME-OF-FLIGHT METHOD

Citation Formats

Wei Peiying, Chang Yuanping, Lee Yushan, Lee Weibin, Lin Kingchuen, Chen, K. T., Chang, A. H. H., and Department of Chemistry, National Dong Hwa University, Shoufeng, Hualien 974, Taiwan. Br{sub 2} molecular elimination in 248 nm photolysis of CHBr{sub 2}Cl by using cavity ring-down absorption spectroscopy. United States: N. p., 2007. Web. doi:10.1063/1.2426334.
Wei Peiying, Chang Yuanping, Lee Yushan, Lee Weibin, Lin Kingchuen, Chen, K. T., Chang, A. H. H., & Department of Chemistry, National Dong Hwa University, Shoufeng, Hualien 974, Taiwan. Br{sub 2} molecular elimination in 248 nm photolysis of CHBr{sub 2}Cl by using cavity ring-down absorption spectroscopy. United States. doi:10.1063/1.2426334.
Wei Peiying, Chang Yuanping, Lee Yushan, Lee Weibin, Lin Kingchuen, Chen, K. T., Chang, A. H. H., and Department of Chemistry, National Dong Hwa University, Shoufeng, Hualien 974, Taiwan. Sun . "Br{sub 2} molecular elimination in 248 nm photolysis of CHBr{sub 2}Cl by using cavity ring-down absorption spectroscopy". United States. doi:10.1063/1.2426334.
@article{osti_20868216,
title = {Br{sub 2} molecular elimination in 248 nm photolysis of CHBr{sub 2}Cl by using cavity ring-down absorption spectroscopy},
author = {Wei Peiying and Chang Yuanping and Lee Yushan and Lee Weibin and Lin Kingchuen and Chen, K. T. and Chang, A. H. H. and Department of Chemistry, National Dong Hwa University, Shoufeng, Hualien 974, Taiwan},
abstractNote = {Elimination of molecular bromine is probed in the B {sup 3}{pi}{sub ou}{sup +}<-X {sup 1}{sigma}{sub g}{sup +} transition following photodissociation of CHBr{sub 2}Cl at 248 nm by using cavity ring-down absorption spectroscopy. The quantum yield for the Br{sub 2} elimination reaction is determined to be 0.05{+-}0.03. The nascent vibrational population ratio of Br{sub 2}(v=1)/Br{sub 2}(v=0) is obtained to be 0.5{+-}0.2. A supersonic beam of CHBr{sub 2}Cl is similarly photofragmented and the resulting Br atoms are monitored with a velocity map ion-imaging detection, yielding spatial anisotropy parameters of 1.5 and 1.1 with photolyzing wavelengths of 234 and 267 nm, respectively. The results justify that the excited state promoted by 248 nm should have an A{sup ''} symmetry. Nevertheless, when CHBr{sub 2}Cl is prepared in a supersonic molecular beam under a cold temperature, photofragmentation gives no Br{sub 2} detectable in a time-of-flight mass spectrometer. A plausible pathway via internal conversion is proposed with the aid of ab initio potential energy calculations. Temperature dependence measurements lend support to the proposed pathway. The production rates of Br{sub 2} between CHBr{sub 2}Cl and CH{sub 2}Br{sub 2} are also compared to examine the chlorine-substituted effect.},
doi = {10.1063/1.2426334},
journal = {Journal of Chemical Physics},
number = 3,
volume = 126,
place = {United States},
year = {Sun Jan 21 00:00:00 EST 2007},
month = {Sun Jan 21 00:00:00 EST 2007}
}